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Date:   Thu, 1 Oct 2020 22:27:03 +0200
From:   Petr Vorel <petr.vorel@gmail.com>
To:     Rich Felker <dalias@aerifal.cx>
Cc:     linux-kernel@vger.kernel.org, musl@lists.openwall.com,
        linux-api@vger.kernel.org, libc-alpha@sourceware.org,
        Peter Korsgaard <peter@korsgaard.com>,
        Florian Weimer <fweimer@redhat.com>,
        Baruch Siach <baruch@tkos.co.il>,
        "David S . Miller" <davem@davemloft.net>,
        Michal Kubecek <mkubecek@suse.cz>,
        Stephen Hemminger <stephen@networkplumber.org>
Subject: Re: [musl] [PATCH 1/1] uapi: Don't include <linux/sysinfo.h> in
 <linux/kernel.h>
Message-ID: <20201001202703.GD24195@dell5510>
Reply-To: Petr Vorel <petr.vorel@gmail.com>
References: <20201001195231.17226-1-petr.vorel@gmail.com>
 <20201001201108.GR17637@brightrain.aerifal.cx>
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Hi Rich,

> On Thu, Oct 01, 2020 at 09:52:31PM +0200, Petr Vorel wrote:
> > + update code where needed (include <linux/sysinfo.h> in code which
> > included <linux/kernel.h> only to get struct sysinfo or SI_LOAD_SHIFT).

> > The reason is to avoid indirect <linux/sysinfo.h> include when using
> > some network headers: <linux/netlink.h> or others [1] ->
> > <linux/kernel.h> -> <linux/sysinfo.h>.

> > This indirect include causes redefinition of struct sysinfo when
> > included both <sys/sysinfo.h> and some of network headers:

> > In file included from x86_64-buildroot-linux-musl/sysroot/usr/include/linux/kernel.h:5,
> >                  from x86_64-buildroot-linux-musl/sysroot/usr/include/linux/netlink.h:5,
> >                  from ../include/tst_netlink.h:14,
> >                  from tst_crypto.c:13:
> > x86_64-buildroot-linux-musl/sysroot/usr/include/linux/sysinfo.h:8:8: error: redefinition of ‘struct sysinfo’
> >  struct sysinfo {
> >         ^~~~~~~
> > In file included from ../include/tst_safe_macros.h:15,
> >                  from ../include/tst_test.h:93,
> >                  from tst_crypto.c:11:
> > x86_64-buildroot-linux-musl/sysroot/usr/include/sys/sysinfo.h:10:8: note: originally defined here

> > [1] or <linux/sysctl.h>, <linux/ethtool.h>, <linux/mroute6.h>, <linux/ethtool.h>

> > Suggested-by: Rich Felker <dalias@aerifal.cx>
> > Signed-off-by: Petr Vorel <petr.vorel@gmail.com>
> > ---
> > Hi,

> > this looks to be long standing problem: python-psutil [2], iproute2 [3],
> > even for glibc in the past [4] and it tried to be solved before [5].

> > This will require glibc fix after:

> You can't do this; it breaks the existing contract with glibc. New
> kernel headers can't force a glibc upgrade.
Right, got that.

> You just have to get rid
> of use of <linux/kernel.h> elsewhere in the uapi headers. It was a
> mistake that <linux/sysinfo.h> was ever separated out of
> <linux/kernel.h> since it didn't (and couldn't) fix the contract that
> <linux/kernel.h> exposes struct sysinfo (and that it's misnamed). But
> it's no big deal. This can all be fixed without any breakage anywhere
> just by not using it.
Back to your original suggestion to move the alignment macros to a separate
header. I was trying to avoid it not sure if introducing new header is
acceptable, but we'll see.

> Rich

Kind regards,
Petr